1. Field of the Invention
The present invention relates generally to machine tools and more particularly, to an apparatus for machining an end surface of one of a pair of matchable parts by reference to a reference surface of the other part in a state that the parts are mutually combined.
2. Description of the Prior Art
A machining system under a so-called matching control has heretofore been known, in which, for the purpose of enhancing fitting accuracy of a pair of parts to be mutually matched or combined, an inside diameter of one of the parts is measured by a post-process gauge while an outside diameter of the other part in process is measured by an in-process gauge, and feed movement of a machining tool is controlled to make constant the difference between the sizes measured by both the gauges. In such a known system, the surface of the one part to be machined is determined to be a fitting surface into a reference internal surface of the other part, and the fitting accuracy of the parts can be satisfied since the external surface is machined while being compared with the reference internal surface in size of diameter.
However, the known system is impossible to use in the case where one of the parts is engaged with the other part at a surface other than an external surface thereof to be machined and where the other part has a reference surface independently of an engagement surface thereof. In this case, there is conceivable the use of another machining system, wherein the other part is positioned outside the machine in a suitable manner for measurement of the reference surface by a post-process gauge, while the surface of the one part in process is measured by an in-process gauge so that feed movement of a tool is controlled to bring about coincidence between measurement signals from both the gauges. According to this system, compensation can be made for a size dispersion of engagement surfaces relative to reference surfaces of the other parts. The system, however, falls into a meaningless one because one of the parts, respectively pairing with the other of the parts, also has a disparity with the positions of engagement surfaces relative to surfaces thereof to be machined.
Another system is further conceivable which measures a size from a surface in process to an engagement surface of one of the parts as well as a size from a reference surface to a fitting surface of the other part and which controls feed movement of a machining tool to make constant the difference between both the sizes. This system is, however, impractical since it requires the use of two sizing devices for each part and, depending upon the kind of workpieces, increases the difficulty in measuring the positions of two surfaces on each part.